用有限元法计算飞秒激光双光子成型点弹性模量

采用有限元法对材料为SCR500的飞秒激光双光子成型点力学性能进行建模及仿真计算，得出了不同弹性模量下成型点与探针之间的作用力．进而利用原子力显微镜接触模式，选用无针尖探针，测量了成型点的力学性能，得出了相同位移载荷下成型点与探针之间的作用力．将测量结果和仿真结果进行比较，推算出成型点的弹性模量．分析结果表明。双光子固化成型点的弹性模量大约为宏观材料弹性模量的1／7．这为进一步研究双光子飞秒激光加工微器件的力学性能提供了基础．     

飞秒激光三维微细加工技术

双光子吸收几率与光强度的平方成正比,因此,双光子吸收引发光致聚合局限在紧密聚焦的焦点区域,通过控制焦点的扫描运动可实现高精度三维加工。基于该原理,提出了一种利用飞秒激光进行微细加工的技术。根据此技术,建立了飞秒激光三维微细加工系统,该系统包括光源系统、显微镜系统、实时监测系统和精密移动系统等。研究发现,该系统加工的直线线宽最小可达500nm;加工线宽与加工速度成反比;激光功率为2mW时,最大和最小临界加工速度分别为80μm/s和1μm/s;制备出线宽1μm,宽度5μm的“CHINA”复杂结构,以及杆间距、层间距均为5μm的三维木堆型光子晶体结构。实验证实,该技术是一种非常灵活的微细加工技术。     

原子力显微镜在高分子薄膜领域的应用

介绍了原子力显微镜(AFM)在高分子薄膜领域中的最新应用技术。在定位观察薄膜时,可采用碳纳米管定位法以及针尖打孔定位法对所观察的样品进行定位,该方法可实现对样品进行离位处理之后再次精确定位。在测量高分子薄膜厚度时,可采用针尖打孔法和漂膜法通过制备断面台阶利用AFM精确测量薄膜厚度。基于特殊相分离形貌的嵌段共聚物薄膜,可采用AFM针尖对其表面进行锻造纳米加工。这些技术拓展了AFM在聚合物薄膜表征以及纳米加工等领域的应用。     

利用典型Si(100)微结构对原子力显微镜探针参数进行表征

利用各向异性化学湿法刻蚀工艺在Si(100)上加工了具有本征侧墙角(54.73°)的典型微机电系统(MEMS)梯形结构.用该微结构作为线宽测试结构,对其进行了原子力显微镜(AFM)和扫描电子显微镜(SEM)线宽和轮廓的比对测量.并对AFM探针和样品耦合效应进行了研究,提出了AFM探针参数动态表征的模型,基于几何模型对线宽和轮廓测量中探针针尖形状和针尖位置参数进行了表征,提出了用曲率半径、安装倾角、扫描倾角和针尖半顶角来对原子力显微镜探针针尖进行表征.该方法是对现有AFM探针表征模型的改进和完善.     

飞秒激光烧蚀血管支架材料的数值模拟

为了研究飞秒脉冲激光烧蚀血管支架材料的特性,利用考虑了电子之间热传导项的双温模型,采用有限差分法,对飞秒激光烧蚀NiTi合金的温度场分布进行数值模拟,计算得到了电子温度和晶格温度随时间和烧蚀深度的变化规律,进一步讨论了不同激光能量密度、不同激光脉宽、不同延迟时间对电子和晶格的温度场影响。发现血管支架材料在飞秒激光的作用下,先是电子吸收能量温度快速升高,再通过电声耦合作用将能量传递给晶格,最后两者的温度达到一个平衡状态;激光能量密度主要影响电子的峰值温度和电子与晶格的平衡温度;脉冲宽度主要影响电子的峰值温度和达到峰值温度所用的时间;电子温度随着延迟时间的增加先升高后降低,晶格温度随着延迟时间的增加不断上升。这些理论分析对实际飞秒激光加工血管支架有重要的指导意义。     

基于激光诱导表面周期结构的微纳防伪结构色

激光诱导表面周期结构由于其周期相关的光栅衍射特性在明场下显示出鲜艳的结构色,备受研究人员的广泛关注,而微纳结构在显微镜暗场显示的颜色通常容易被忽略.本文报道通过飞秒激光对氧化铟锡薄膜加工形成双周期光栅结构,利用其在明场和暗场的观察下具有不同的颜色特性实现图像加密应用.通过控制飞秒激光的偏振、脉冲能量和扫描速度在氧化铟锡...     

针尖力学——原子力显微镜(AFM)中的纳米力学

原子力显微镜已在材料、医学、生化、精密加工与组装、原子及分子操纵等学科领域内取得了广泛应用。该文以原子力显微镜成像机理与应用研究为背景,提出了针尖力学的概念。介绍了原子力显微镜的应用前沿,阐述了针尖力学的研究方法与研究现状,点明了多学科跨尺度方法在针尖力学研究中的应用前景。     

极浅压入下纳米压痕仪针尖面积函数校准方法的研究

采用原子力显微镜直接扫描纳米压痕仪针尖法、球面拟合法和熔融石英标准样块的间接测量法对极浅压入下纳米压痕仪的针尖面积函数进行比较分析。实验表明,在极浅压入下,原子力显微镜直接法由于真实地反映了针尖尖端的几何形貌因而获得的面积函数更为准确可靠。建立了相应的数学模型,对于直接法测量中主要的误差,即由于原子力显微镜针尖曲率半径带来的误差进行了分析,结果表明在极小压入深度下压入深度越小,原子力显微镜针尖曲率半径带来的压痕仪针尖面积函数相对误差越大。     

用SPM纳米刻蚀方法在Ti表面制备纳米结构的研究

本文用导电原子力显微镜 (AFM)针尖诱导局域氧化反应的方法 ,在Ti膜表面制备了TiO2 纳米结构。实验结果表明 ,Ti膜的氧化阈值为 - 7伏 ,制备的TiO2 纳米线的最小线宽达到 10nm ,TiO2 纳米线的高度和宽度随针尖偏压的增大而增大。在优化的氧化刻蚀条件下 ,通过控制针尖偏压和扫描方式制备出了图形化的TiO2 结构 ,本研究表明基于导电AFM的纳米刻蚀技术将成为构筑纳米电子器件的重要工具     

脉冲激光沉积法室温下ZnO薄膜的制备与表征

在室温条件下,采用脉冲激光沉积技术在玻璃衬底上生长了ZnO薄膜.对薄膜的XRD分析表明,ZnO薄膜为六方纤锌矿结构并沿c轴取向生长,且(002)衍射峰的半高峰宽仅为0.24°.薄膜沿c轴方向受到一定的张应力为1.7×108 N/m2.原子力显微镜分析表明薄膜表面较为平整,平均粗糙度约为6.5 nm,晶粒尺寸约为50 nm.此外,透射光谱分析表明薄膜的禁带宽度为3.25 eV,与ZnO体材料的禁带宽度3.30 eV基本相同.     

Femtosecond Laser Fabrication of Cavity Microball Lens (CMBL) inside a PMMA Substrate for Super‐Wide Angle Imaging

Since microlenses have to date been fabricated primarily by surface manufacturing, they are highly susceptible to surface damage, and their microscale size makes it cumbersome to handle. Thus, cavity lenses are preferred, as they alleviate these difficulties associated with the surface‐manufactured microlenses. Here, it is shown that a high repetition femtosecond laser can effectively fabricate cavity microball lenses (CMBLs) inside a polymethyl methacrylate slice. Optimal CMBL fabrication conditions are determined by examining the pertinent parameters, including the laser processing time, the average irradiation power, and the pulse repetition rates. In addition, a heat diffusion modeling is developed to better understand the formation of the spherical cavity and the slightly compressed affected zone surrounding the cavity. A micro‐telescope consisting of a microscope objective and a CMBL demonstrates a super‐wide field‐of‐view imaging capability. Finally, detailed optical characterizations of CMBLs are elaborated to account for the refractive index variations of the affected zone. The results presented in the current study demonstrate that a femtosecond laser‐fabricated CMBL can be used for robust and super‐wide viewing micro imaging applications.     

Atomic force microscopy tip torsion contribution to the measurement of nanomechanical properties

The nanomechanical properties of polymethyl methacrylate and indium phosphide were measured with an atomic force microscope and a nanoindentation system. The elastic moduli measured with the atomic force microscope are in good agreement with the values obtained with the nanoindentation system. The hardness is shown to be affected by the tip radius used in our experiments. The cantilever vertical and lateral movements were independently analyzed during nanoindentation, and the tip torsion can be attributed to a change from elastic to plastic deformation regimes of materials during force microscopy nanoindentation. An analysis of the lateral movement of the laser beam associated with the cantilever torsion was used to determine the material yield stress.     

颅骨修复复合材料的制备

主要论述了碳纤维 (CF)和玻璃纤维 (GF)混杂增强聚甲基丙烯酸甲酯 (PMMA) /羟基磷灰石 (HA)复合材料人工颅骨的制备方法及其力学性能。通过实验 ,证实了此复合材料具有比单纯GF增强PMMA/HA复合材料人工颅骨更好的物理机械性能 ,是目前制作人工颅骨较为理想的材料。     

A Smart Procedure for the Femtosecond Laser-Based Fabrication of a Polymeric Lab-on-a-Chip for Capturing Tumor Cell

Rapid prototyping methods for the design and fabrication of polymeric labs-on-a-chip are on the rise, as they allow high degrees of precision and flexibility. For example, a microfluidic platform may require an optimization phase in which it could be necessary to continuously modify the architecture and geometry; however, this is only possible if easy, controllable fabrication methods and low-cost materials are available. In this paper, we describe the realization process of a microfluidic tool, from the computer-aided design (CAD) to the proof-of-concept application as a capture device for circulating tumor cells (CTCs). The entire platform was realized in polymethyl methacrylate (PMMA), combining femtosecond (fs) laser and micromilling fabrication technologies. The multilayer device was assembled through a facile and low-cost solvent-assisted method. A serpentine microchannel was then directly biofunctionalized by immobilizing capture probes able to distinguish cancer from non-cancer cells without labeling. The low material costs, customizable methods, and biological application of the realized platform make it a suitable model for industrial exploitation and applications at the point of care.     

碳纳米管／聚氨酯纳米复合材料的制备及性能

采用可逆加成-断裂链转移(RAFT)聚合方法在碳纳米管表面接枝聚甲基丙烯酸甲酯和聚苯乙烯嵌段共聚物MWNT-P(MMA-b-St),对碳纳米管进行改性。采用直接共混法制备碳纳米管/水性聚氨酯纳米复合材料。通过红外光谱(FT-IR)和透射电镜(TEM)对嵌段共聚物的结构进行了表征。碳纳米管加入对乳液成膜性影响不大。热失重分析(TGA)和力学性能测试结果表明,当改性后的碳纳米管含量为聚氨酯固体份的0.75%时,复合材料的热稳定性、拉伸强度和断裂伸长率均较聚氨酯有所提高。     

P(MMA-VAc-LiAA)聚合物电解质的制备及表征

以甲基丙烯酸甲酯(MMA)、醋酸乙烯酯(VAc)和丙烯酸锂(LiAA)为单体,采用种子乳液聚合法制备了(P(MMA-VAc-LiAA)三元共聚物.利用红外光谱(FTIR),核磁共振(~1HNMR),差示扫描量热(DSC) /热重分析(TG),X射线衍射(XRD),扫描电镜(SEM)等方法对聚合物的结构进行了表征.将P(MMA-VAc-LiAA)与LiClO_4共混,采用流延法制备了聚合物电解质膜,用交流阻抗方法测试了电解质膜的电导率,结果表明,该聚合物电解质室温离子电导率可以达到10~(-3)S/cm.而且离子电导率随着温度的升高而迅速增加,电导率-温度曲线符合Arrhenius方程.机械性能测试结果表明,在P(MMA-VAc)的基础上,引入第三单体LiAA可以改善膜的收缩性与力学性能.     

The shape effect of Au particles on random laser action in disordered media of Rh6G dye doped with PMMA polymer

Abstract

Random laser actions in a disordered media based on polymethyl methacrylate (PMMA) polymer doped with Rh6G dye and Au nanoparticles have been demonstrated. It was observed that the shape of Au nanoparticles can tune the spectral central position of the random laser action. It was also seen that the shape of Au nanoparticles strongly affects the pump threshold. Comparing nanosphere- and nanorod-based systems, the nanorod-based one exhibited a lower threshold.     

Floating tip nanolithography

We demonstrate noncontact, high quality surface modification of soft and hard materials with spatial resolution of approximately 20 nm. The nanowriting is based on the interaction between the surface and the tip of a standard atomic force microscope illuminated by a focused femtosecond laser beam and hovering (at ambient conditions) 1-4 nanometers above the surface without touching it. Field enhancement at the tip-sample gap or high tip temperature are identified as the causes of material ablation.     

RAFT聚合方法在碳纳米管表面接枝嵌段共聚物

首先在碳纳米管表面接上可用做RAFT聚合的链转移剂——二硫代碳酸酯,然后用这些管壁接有二硫代碳酸酯的碳纳米管作为链转移剂引发甲基丙烯酸甲酯和苯乙烯单体进行可控的嵌段聚合反应,首次报道了采用二步加料方式在碳纳米管的管壁上接枝上嵌段共聚物链。对嵌段共聚物的结构进行了红外光谱(FT-IR)、热重分析(TGA)、透射电镜(TEM)表征。     

Experimental study of crack propagation in polymethyl methacrylate material with double holes under the directional controlled blasting

The crack propagation behaviours of polymethyl methacrylate material with double holes under the directional controlled blasting are studied using dynamic caustic method. A series of dynamic caustic patterns at the propagating crack tip under the explosive loading are recorded using the digital high‐speed camera. Some important dynamic fracture characterizations and parameters about two main cracks are determined including the crack path, the propagating speed and the crack tip stress intensity factors. The fracture mechanisms of the double blasting holes are analysed. The results provide the important experimental basis for evaluating and designing the directional controlled blasting for the rock tunnel and the rock face excavation.